The present invention relates to a mechanism of a manual transmissin for preventing gear clashing which is liable to occur when the transmission is shifted into reverse speed engagement.
In manual transmissions in general, the shift into reverse is unsynchronized, so that the reverse ' speed shift is liable to be noisy. Conventional mechanisms to avoid such a gear noise by using a synchronizer for forward speed are disclosed in Japanese patent provisional publication No. 57-137747, Japanese patent post-examination publication No. 59-14655, and U.S. Pat. No. 3,545,295.
These conventional mechanisms are arranged to actuate a forward speed synchronizer by transmitting a reverse shift movement of a driver's hand shift lever to the forward speed synchronizer through a pin and spring assembly, which causes such a result that an operating force for actuating the forward speed synchronizer is proportional to a biasing force of the spring. Accordingly, the magnitude of the operating force applied to the forward speed synchronizer is increased and decreased in dependence on the speed of the shift movement of the hand shift lever. For example, when the hand shift lever is shifted rapidly with a great force, the operating force is too weak to actuate the synchronizer, so that the speed of the transmission counter shaft cannot be decreased sufficiently and the gear noise cannot be prevented reliably. When, on the other hand, the hand shift lever is shifted slowly, the hand shift lever becomes so heavy that a large force is required to shift the lever.
Another similar conventional mechanism is shown in "Toyota Gijutsu (technique)", Vol. 38, No. 2, page 159, published by Toyota motor Co., Ltd. December, 1983. U.S. Pat. No. 4,294,338, and Japanese patent provisional publication No. 59-73650 show still another conventional mechanisms which use a synchronizing mechanism for a fifth speed to facilitate a reverse shift.